Biaxially stretched bottles typified by bottles formed from polyethylene terephthalate (PET) are thinly formed by biaxially stretch blow molding vertically and horizontally from portion below the neck portion of an injection molded preform to a bottom portion thereof. Thus, they are different from thick bottles molded by blowing an ejection molded parison. Moreover, the integral molding of handles on the side portion of a bottle is known to be extremely difficult.
As is described in International Publication No. WO82/02369, attempts have been made during injection molding of the preform to form a transversely long carrying handle integrally with a side of the neck portion and to use this without further modification as a carrying handle for the bottle.
Because these widely known carrying handles are made thick in order to have sufficient strength, and are in a non-stretched state together with the neck portion, when the resin material is a polyester resin, for example, PET, then the handle is hard without sufficient flexibility and is thus difficult to bend. The bottle cannot, therefore, be held hanging vertically.
Furthermore, unstretched PET is deficient in impact strength so that when a bottle fully filled with contents falls from a shelf onto the floor, the handle is sometimes broken.
As a novel means for solving these types of problems in conventional carrying handles, the present inventors achieved the following invention. Base portions projected from opposite positions on either side of a neck portion of a bottle were integrally molded with a U shaped carrying handle formed integrally from a grip portion and arm portions on both sides. This carrying handle extended outwards with a length greater than the height of the neck portion. At the same time, the connecting portions at the boundary of the arm portions and the base portions were molded thinly by constricting the thickness of the connecting portions so that the resin is flow-oriented, thereby the carrying handle could be rotated in a vertical direction from the boundary. Thus breakage of the carrying handles could be prevented.
In this novel carrying handle bottle, even if the carrying handle is facing out to the side, if the bottle is picked up by the carrying handle, the carrying handle naturally bends from the thin connecting portion due to the load of the bottle. The arm portions then rotate upwards so that the carrying handle changes to a vertical orientation giving this carrying handle bottle the advantage that it may be carried substantially vertically. Moreover, because the load when the bottle is carried is concentrated at the connecting portion which is strengthened by the flow orientation of the resin, even if the base portion has an unoriented plate-shaped configuration, there is no breakage caused by the load.
The tensile strength in the connecting portion of the carrying handle is extremely high and is able to sufficiently withstand the weight of even a large size bottle (for example, one having a capacity of 5 liters). There is thus no breakage at all at the boundary or in the base portion (which has a plate thickness of 1.4 mm) caused by the load even after repeated use.
However, if a filled bottle falls from a high place, the phenomenon of cracks appearing in the base portion does sometimes occur. The reason for this is assumed to be that the stress from the impact is concentrated in the neck portion of the bottle and the distortion in the neck portion caused by this acts on the plate-shaped base portion which is connected orthogonally to the vertical neck portion, thus causing the cracks. For this reason, attempts have been made to improve the strength of the base portion by increasing the plate thickness. However, when the plate thickness was increased up to a certain point, the effect achieved did not match that expected. When the plate thickness was then increased even further, a new problem arose in that shrinkage occurred in the surface of the base portion.
The present invention was conceived in order to solve the above described problems and it is an object thereof to provide a biaxially stretched bottle having a new carrying handle, in which the plate-shaped base portion is strengthened against impact force without the actual structure of the carrying handle being altered and has the tensile strength thereof further improved, and which is sufficiently able to withstand use as a large size carrying handle bottle.